Keys for Tropical Medicine 1

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Overview of Tropical Medicine

Definition of the tropics

  • Between the Tropic of Cancer (north latitude 23°26′) and the Tropic of Capricorn (south latitude 23°26′)
  • Covers 40% of land surfaces and 40% of population

Top 3 causes of death in LMICs, HICs and worldwide in 2016

*Bold names are communicable diseases

Worldwide LMICs HICs
  1. Ischemic heart disease
  2. Stroke
  3. Chronic obstructive pulmonary disease (COPD)
  1. Lower respiratory infections
  2. Diarrhea
  3. Ischemic heart disease
  1. Ischemic heart disease
  2. Stroke
  3. Alzheimer and other dementias

Changes of top 10 causes of death worldwide from 2010 to 2016

  • Tuberculosis ranked down to the 10th in 2016 from the 6th in 2010
  • HIV/AIDS ranked down out of 10 in 2016 from the 7th in 2010

List Neglected Tropical Diseases (NTDs) and what are not listed as NTDs

Virus
  1. Dengue & Chikungunya (dengue virus, chikungunya virus)
  2. Rabies (rabies virus)
Bacteria
  1. Buruli ulcer (Mycobacterium ulcerans)
  2. Leprosy (Mycobacterium leprosy)
  3. Trachoma (Chlamydia trachomatis)
  4. Yaws (Treponema pallidum pertenue)
Protozoa
  1. Chagas disease, American trypanosomiasis (Trypanosoma cruzi)
  2. Human African trypanosomyasis, Sleeping sickness (Trypanosoma brucei spp.)
  3. Leishmaniasis (cutaneous and visceral) (Leishmania spp.)
Parasites - Nematodes
  1. Dracunculiasis, Guinea worm (Dracunculus medinensis)
  2. Lymphatic filariasis (Wuchereria bancrofti, Brugia malayi)
  3. Onchocerciasis (Onchocerca volvulus)
  4. Soil-transmitted helminth infections
Parasites - Trematodes
  1. Foodborne trematode infections
  2. Schistosomiasis (Schistosoma spp.)
Parasites -
Cestodes
  1. Echinococcosis (Echinococcus granulosus, E. multilocularis)
  2. Taeniasis/Cysticercosis (Taenia spp.)
Ectoarasites
  1. Scabies, Tungiasis & other ectoparasites (mite, sandflea, etc.)
Fungi
  1. Mycetoma, Chromoblastomycosis (chromomycosis) & other deep mycoses (various spp.)
Non-communicable
  1. Snakebites
  • These are NOT listed as NTDs
    • HIV/AIDS
    • Tuberculosis
    • Malaria
    • Lower respiratory infections
    • Diarrhea

Virus

Two major classification manners of viruses

  • RNA virus vs DNA virus
  • Enveloped virus vs Non-enveloped virus

Diagnostic methods of virus infection

  • Detection of pathogen
    • Genome detection by PCR and other NAATs (nucleic acid amplification tests)
    • Antigen detection by ELISA and immunochromatography, etc.
    • Virus isolation using human/animal cells
  • Detection of antibody
    • IgM or IgG by ELISA and immunochromatography, etc.
    • Neutralizing antibody using human/animal cells

Definition of arboviruses

Classification of major arboviruses and their major vectors

Warning signs of severe dengue

List of Vaccine-preventable arbovirus infections

Essential knowledge of HIV

Watch our Group 4 video and pick up information described in blue letters!

Bacteria

Biological basis of Gram staining

  • Bacteria have both of cell wall and cell membrane
    • Human and other animal cells have no cell wall
    • Plant cells have cell wall
  • Some bacteria have thick cell wall without outer membrane
  • Other bacteria have thin cell wall with outer membrane
  • Cell wall contains a layer of Peptidoglycan
File Bacterial cell walls.jpg
  • Thick peptidoglycan layer catches and keep crystal violet with iodine
  • Outer membrane catches crystal violet with iodine but easily lose them by ethanol rinsing
Gram Stain.png

Classification of major Gram-Positive cocci

Catalase Positive
in tubes		 Coagulase Positive
in tubes		 Coagulase Negative
in tubes
  • Staphylococcus aureus
  • Staphylococcus epidermidis
  • Staphylococcus saprophyticus
Catalase Negative
in tubes		 α hemolytic
(partial hemolysis)
on media		 β hemolytic
(complete hemolysis)
on media		 γ hemolytic
(no hemolysis)
on media
  • Streptococcus pneumoniae
  • Streptococcus suis
  • viridans Streptococcus
  • Group A (beta) streptococci (Streptococcus pyogenes)
  • Group B (beta) streptococci (Streptococcus agalactae)
  • Group C (beta) streptococci
  • Group G (beta) streptococci
  • Streptococcus bovis
  • Enterococcus faecium
  • Enterococcus faecalis

Classification of major Gram-Positive bacilli

Spore forming Non-spore forming
Aerobic
  • Bacillus anthracis
  • Bacillus cereus
  • Corynebacterium diphtheria
Anaerobic
  • Clostridium tetani
  • Clostridium perfringens
  • Listeria monocytogenes

Classification of major Gram-Negative cocci

Classification of major Gram-Negative bacili

Lactose fermenting
  • Escherichia coli
  • Klebsiella pneumoniae
Non-lactose fermenting
  • Shigella spp.
  • Salmonella spp.
  • Yersinia pestis
Non-fermenting
  • Pseudomonas aeruginosa
  • Burkholderia pseudomallei

Essential knowledge of Tuberculosis

  • Bacterial structure different from other major bacteria
    • Too thick lipid-rich cell wall; acid fast
  • Epidemiology and disease burden
  • Three species causing clinical tuberculosis
    • Mycobacterium tuberculosis
    • M. bovis
    • M. africanum (only in Africa)
  • Airborne transmission
    • No contact/fomite transmission
    • Contaminated milk ingestion may cause food-borne tuberculosis by M. bovis (bovis means cow)
  • Three major Symptoms
    • Cough for weeks
    • Weight loss for weeks
    • Night sweats for weeks
  • Diagnostic methods
    • sputum microscopy (Ziel-Nielsen staining)
    • genome detection by GeneXpert (also detects resistance)
    • culture (6-8 weeks)
    • chest X-ray
    • urine LAM assay
    • Mantoux test and IGRA for latent infection
  • Potential of long-term (months, years to decades) infection
    • Human immune system cannot eliminate established infection but only contains (just to 'hide' Mycobacterium)
  • HIV-Tb co-infection is soooooo major public health problem
  • Treatment
    • 6 months (2 intensive + 4 maintenance)
  • Definition of drug resistance
    • MDR
    • XDR

Protozoa

How protozoa differ from bacteria

Classification of major protozoa in terms of reproduction manners and infecting organs/cells

-> Overview_of_protozoa

Essential knowledge of malaria

  • Epidemiology and disease burden of malaria worldwide
    • Especially of Plasmodium falciparum
  • Essential lifecycle
  1. Mosquito stage
  2. Human liver stage
  3. Human red cell stage
  • Only P. vivax and P. ovale have hypnotic stage in liver cause relapse
    • All species cause recrudescence due to inadequate/improper treatment
  • Fever, Anemia, Splenomegaly
  • Cerebral malaria almost only by P. falciparum, which leads to high mortality
  • Diagnosis made by Rapid Diagnostic Test (RDT) and Blood smear microscopy (Giemsa staining)
    • Blood smear includes thick smear (just to detect Plasmodium) and thin smear (confirm species of Plasmodium and degree of parasitemia as disease severity)

Parasite

Major classification of parasites

  • Helminth
    • Nematode (round worm)
    • Trematode (fluke, distoma)
    • Cestode (tape worm)
  • Ectoparasite

Zoonosis

Definition of Zoonosis

List of major zoonoses and their host animals

Disease Pathogen Host animals
Virus Ebola virus disease Ebolavirus Fruit bat
Marburg disease Marburg virus Fruit bat
Middle East Respiratory Syndrome (MERS) MERS coronavirus Camel <- Bat?
Severe Fever with Thrombocytopenia Syndrome (SFTS) SFTS virus Deer, wild bores
Bacteria Anthrax Bacillus anthracis Herbivore (cattle, sheep, goat)
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